Dataone BroadbandI am going to describe a simple no-brainer way to share your BSNL Dataone Broadband internet connection over wireless network. The same principles can be used with other broadband connections too. Here is what you need:
1. A normal non-wireless modem from BSNL which comes with the connection. You can also substitute it with an equivalent ADSL modem from market. Do not purchase the wireless modem from BSNL.
2. A wireless router. I successfully used Linksys WRT54G & Airlink+ routers.

First you need to connect the ethernet cable from the Broadband modem to your router. Connect it to any of the 4 available ports except the uplink port.

Connect the ethernet cable from your computer (it needs to have a ethernet card) to another port of the wireless router. Alternatively you can connect to the router over wireless. Change the IP address of your computer to 192.168.1.x and the subnet mask to 255.255.255.0. Do not specify any DNS or gateway address.

Now you can either configure your ADSL modem to automatically connect to the internet when switched on or you can use your computer to connect to the internet.

Please follow the steps to configure your ADSL modem to automatically connect to the internet in the linked article. This also automatically reconnects when the connection goes down and comes up again. In this setup all your computers will have direct access to the internet. So you should install a firewall on each computer. This is the simplest setup. The downside is that it is not as responsive to frequent connects and disconnects as you would like. It takes some time after the connection is restored to connect again.

The other alternative is to use your computer to initiate the connection. Windows users should install the accompanying software to connect to the internet. It will correctly detect the connection over a LAN or wireless connection in the above mentioned setup.

Linux users please follow the guide to connect to internet from Linux with BSNL DataOne Broadband.

In this setup you have to either setup a proxy server on the machine initiating the connection to the internet or setup a firewall cum gateway like Firestarter (Linux). I use this setup and I use Firestarter. This allows unrestricted but protected access to the internet. All the traffic is routed from the same machine so it is easy to setup firewall rules for traffic monitoring and protection.

After you are done I suggest that you read on few tips to improve your BSNL DataOne broadband speed.

Caution: I still hold to the opinion that BSNL DataOne is the world's crappiest broadband service primarily because of frequent unavailability and pratically non-existent customer support.